NEW YORK – Buoyant gay couples cheered by supporters began marrying Sunday on the landmark day that New York became the sixth and largest U.S. state to recognize same-sex weddings and provided fresh energy to the national gay rights movement.

New York's adoption of legal same-sex marriage is viewed as a pivotal moment in the national gay rights movement and was expected to galvanize supporters and opponents alike. The state joined Connecticut, Iowa, Massachusetts, New Hampshire and Vermont, along with Washington, D.C., when it voted last month to legalize gay marriage.

Protest rallies were planned in Manhattan, Buffalo, Rochester and Albany on Sunday afternoon. Gay marriage opponents unhappy that Gov. Andrew Cuomo and lawmakers legalized same-sex marriage last month are calling for a statewide referendum on the issue.

Same-sex couples began exchanging vows at midnight from Niagara Falls to Long Island, though the center of the action was in New York City, where officials expected to host hundreds of same-sex weddings throughout the day. About 100 couples waited in line on a sweltering morning in Manhattan for the chance to exchange vows at the city clerk's office.

Some people waiting to wed clutched bouquets and wore tuxedos or wedding dresses before they were ushered into the clerk's office for a license and a ceremony in one of the building's simple chapels.

The first couple to marry in Manhattan were Phyllis Siegel, 76, and Connie Kopelov, 84, who have been together for 23 years. Kopelov arrived in a wheelchair and stood with the assistance of a walker. During the service, Siegel wrapped her hand in Kopelov's hand and they both grasped the walker

Witnesses cheered and wiped away tears after the two women vowed to "honor and cherish" each other as spouses and then kissed.

"I am breathless. I almost couldn't breathe," Siegel said after the ceremony. "It's mind-boggling. The fact that's it's happening to us -- that we are finally legal and can do this like everyone else."

Outside afterward, Siegel raised her arms exultantly as Kopelov, in a wheelchair, held out a marriage certificate.

Also in the first wave of couples to say "I do" in Manhattan were Daniel Hernandez, 53, and Nevin Cohen, 48, Manhattan residents who met in 1998. The two men, wearing matching navy sport jackets, kissed as a group of four friends clapped and news photographers' cameras snapped.

"It feels great," said Hernandez after the ceremony. "To have achieved this in my lifetime and see so many couples who have been loved and living together, to see them finally become part of a greater community of loving couples is phenomenal."

Clerks in New York City and about a dozen other cities statewide opened their doors Sunday to cater to same-sex couples. In New York City and other locations, judges waived a mandatory 24-hour waiting period that allowed couples to exchange vows moments after receiving their licenses.

In Farmingville on Long Island, Steven Hammer, 46, and Joe Lobosco, 63, were among the steady flow of people showing up for a license. The residents of Ridge, New York, were married in Canada eight years ago, but opted for another ceremony in their home state.

"After 21 years together, we're not going to get cold feet," Hammer said. "It justifies everything we've been living for 21 years."

First in line across the state in Buffalo were Daniel Rodgers, 54, and Scott Klaurens, 40, who were married in shorts, T-shirts and sneakers. They had gone expecting only to get a license and planned to wed Tuesday, but were told they could go ahead Sunday because of their marriage six years ago in Toronto.

"This morning has been like a flower opening up," Rodgers said "This is just a flower opening up for us and everyone else, a flower of equality."

Initially, New York City officials had projected that about 2,500 couples might show up at the city clerk's offices hoping to get married on Sunday, but by the time a 48-hour lottery had drawn to a close on Thursday, 823 couples had signed up -- 59 more than the city had planned to accommodate. The city will perform ceremonies for all 823.

A party atmosphere reigned in the lobby of the Manhattan clerk's office. Cheers and applause broke out whenever a couple was handed their white-and-blue wedding certificate. Balloons floated overhead. One couple wore matching kilts; another wore sparkly crowns. Children scurried up and down the lobby; workers with bullhorns called out the numbers of each couple.

Couples posed for pictures in front of a photo backdrop of City Hall and bought T-shirts saying "I got married in New York City" from the clerk's office gift shop.

There were some glitches, though. In Brooklyn, Eufemio Torres and John Torres were told incorrectly by a city employee that they could not wed Sunday because Eufemio had only a Mexican passport.

"Our hearts sank. But I'm a fighter, and we were not going home," said John Torres, a legal secretary.

Soon after speaking with the Brooklyn borough president's chief of staff, the pair stood before a judge in the hall's elaborately wood-carved main chamber. Eufemio Torres cradled a bouquet of white lilies and orchids, and the men took their wedding vows.

In Niagara Falls, gay-rights activists Kitty Lambert and Cheryle Rudd were legally married the very first moment they could be during a midnight ceremony at a traditional setting for weddings.

With the rainbow-lit falls as a backdrop, Lambert, 54, and Rudd, 53, were among the first gay couples to tie the knot with the blessing of the state. Lambert and Rudd, who have 12 grandchildren between them, have been together for more than a decade and had long been fighting for the right to marry.

The couple, both from Buffalo, smiled broadly as they exchanged traditional marriage vows, promising to love and cherish each other in sickness and in health. A crowd of several hundred people cheered as they were pronounced married and shared their first kiss.

"What an incredible night this was," said Lambert, who wore an electric blue satin gown with a sequined train for the ceremony and carried a bouquet of blue hydrangeas. " Everything was absolutely perfect."

In Albany, Mayor Jerry Jennings performed marriages at 12:01 a.m. Sunday in the Common Council's chambers.